A family of main-chain polymeric Lewis acids: Synthesis and fluorescent sensing properties of boron-modified polythiophenes

A new family of main-chain organoborane polymeric Lewis acids (PTh-BAr) that contain Lewis acidic boron groups embedded into a polythiophene backbone has been prepared under mild conditions through tin-boron exchange reaction. When phenyl and pentafluorophenyl groups are attached to boron, blue and green luminescence is observed, respectively, while the attachment of ferrocenyl substituents leads to a characteristic red color. The incorporation of readily accessible highly Lewis acidic groups into the conjugated polymer backbone provides an opportunity for sensing of Lewis basic substrates. For instance, treatment of the polymer containing phenyl substituents on boron with pyridine leads to efficient quenching of the fluorescence, while the polymer containing ferrocenyl groups changes color from dark red to light orange.